Carbazole-modified conjugated column[5]arene derivatives and their synthesis and application in iodine adsorption separation

Abstract

The present invention discloses a carbazole-modified conjugated pillar[5]arene derivative, which is obtained by Suzuki coupling reaction of a carbazole compound having a π conjugated group with pillar[5]arene. Compared with conventional unmodified ethoxylated pillar[5]arene, the structure is transformed from a non-porous structure to a porous structure, and the specific surface area is greatly increased. One-dimensional pores are also formed in the stacking mode. It can be used as a new adsorbent to adsorb iodine. It can not only adsorb iodine vapor, but also adsorb iodine from organic solvents or water. Compared with previously reported iodine adsorbents, the synthesis of carbazole-modified ethoxylated pillar[5]arene is very simple and the raw materials are extremely cheap. Iodine is easily soluble in organic solvents, so the adsorbed iodine can be released in the organic solvent and can be reused multiple times. Therefore, it is expected to be used as a new adsorbent in the future for the selective adsorption and separation of certain specific components in the environment such as environmental pollutants, precious metals and nuclear waste.

Description

Technical Field

[0001] The present invention relates to a conjugated column [5] aromatic hydrocarbon derivative and a synthesis method thereof. The present invention also relates to the application of the conjugated column [5] aromatic hydrocarbon derivative as an adsorption material in adsorption separation, belonging to the technical fields of compound synthesis and adsorption material technology. Background Art

[0002] As a clean and efficient energy source, nuclear power has attracted much attention in meeting the world's growing energy demand and carbon neutrality goals. However, since the accidents at the Fukushima Nuclear Power Plant in Japan and the Chernobyl Nuclear Power Plant in the Soviet Union, how to use nuclear energy safely and effectively has become the focus of attention of many scientific researchers. As radioactive waste, especially volatile and metabolic-related radioactive nuclides iodine. Among them, iodine (129) has a long radioactive half-life (1.57×10 7 years), and in the nuclear industry production process, iodine (129) is a very common nuclear waste, so its adsorption and storage are very important. In addition, iodine (131) has a short half-life (8.02 days) and has side effects on human metabolism, so it should accumulate rapidly. Capturing iodine requires in-depth design of eco-friendly and economical materials. Most of the porous organic metal frameworks currently studied can also be used as iodine adsorption materials, but their relatively low thermal stability and humidity stability limit their practical application, because nuclear power plants contain a large amount of water vapor and the temperature of volatile nuclear waste is usually relatively high. Therefore, the development of new adsorbents with high iodine capture capacity and strong chemical and thermal stability remains a challenge.

[0003] Pillarene, as a new class of supramolecular host compounds, has demonstrated excellent results in host-guest chemistry. By modifying the structure of pillarene, many host-guest chemical systems have been well developed. Pillar[5]arene provides a good macrocyclic cavity structure, so it has a certain assembly ability and can be used to encapsulate small guest molecules. The present invention found through N2 adsorption isothermal test and cultured single crystal structure that compared with the traditional unmodified fully ethoxy pillar[5]arene, the carbazole-modified ethyl pillar[5]arene has changed from a non-porous structure to a porous structure, and has greatly increased the specific surface area. It also forms a one-dimensional pore in the stacking mode. Thermogravimetric test experiments also show that it has good thermal stability and can be used as a new adsorption material to capture iodine. It can not only adsorb iodine vapor in the air, but also adsorb iodine from organic solvents or water. Compared with previously reported iodine adsorption materials, the synthesis of carbazole-modified ethoxy pillar[5]arene is very simple and the raw materials are relatively cheap, and the thermal stability is high; iodine is easily soluble in organic solvents, so the adsorbed iodine can be released in organic solvents, and it can be reused many times. Summary of the Invention

[0004] The purpose of the present invention is to provide a carbazole-modified conjugated column [5] aromatic derivative and a synthesis method thereof;

[0005] Another object of the present invention is to provide a carbazole-modified conjugated column [5] aromatic hydrocarbon derivative for use as an adsorption material in iodine capture.

[0006] 1. Carbazole-modified column [5] aromatic derivatives and their synthesis methods

[0007] The structural formula of the carbazole-modified column[5] aromatic derivative is:

[0008]

[0009] Pillar[5]arene derivatives are synthesized by Suzuki coupling of trifluoromethanesulfonate-modified pillar[5]arene (P5-OTf) with 4-(9H-carbazol-9-yl)phenylboronic acid to obtain carbazole-modified conjugated pillar[5]arene derivatives as white solids, labeled P5CBZ. The specific synthesis method is as follows:

[0010] Synthesis of carbazole-modified conjugated column [5] aromatic derivative P5CBZ: Using toluene, ethanol and water as a mixed solvent, tetrakis(triphenylphosphine)palladium, lithium bromide and potassium carbonate as co-catalysts, the intermediate compound P5-OTf and 4-(9H-carbazole-9-yl)phenylboronic acid are refluxed at 95-105°C for 24-36 hours under nitrogen protection at a molar ratio of 1:2.0~1:2.4, dissolved in distilled water, extracted with dichloromethane, dried over anhydrous sodium sulfate, and the organic phase separated by column chromatography to obtain a white solid, which is the conjugated column [5] aromatic derivative P5CBZ.

[0011] The amount of tetrakis(triphenylphosphine)palladium used is 0.1 to 0.2 times the molar amount of the intermediate compound; the amount of lithium bromide used is 0.2 to 0.3 times the molar amount of the intermediate compound; and the amount of potassium carbonate used is 8 to 12 times the molar amount of the intermediate compound. The volume ratio of toluene, ethanol, and water in the mixed solvent is 8:1:1.

[0012] The structural formula of pillar[5]arene trifluoromethanesulfonate (P5-OTf) is:

[0013]

[0014] Column [5] Aryl trifluoromethanesulfonate (P5-OTf) is from the literature: Adv. Mater. 2018, 30,1800177.

[0015] 2. Characterization of Pillar[5] Arene Derivatives

[0016] (1) Cultivation of single crystals

[0017] Single crystals of the column[5]arene derivative P5CBZ were grown in dichloromethane solution, and the crystal packing pattern was analyzed ( Figure 1 ). It was found that a one-dimensional pore channel was formed in the stacking mode, which achieved a transition from a non-porous structure to a porous structure compared to the traditional unmodified fully ethoxylated pentaaromatic hydrocarbon.

[0018] (2) Low-temperature nitrogen adsorption-desorption isotherm test

[0019] The crystal porosity of P5CBZ crystals and EtP5 crystals in N2 adsorption / desorption isothermal experiments at 77 K, as well as the apparent BET surface area of ​​the two crystals, the pore distribution, pore contribution rate and pore volume of the crystals calculated by the BJH model, were measured and systematically compared. Through comparative analysis, it was found that compared with the traditional unmodified fully ethoxylated pillar[5]arene, the carbazole-modified ethoxylated pillar[5]arene achieved a transition from a non-porous structure to a porous structure, and greatly increased the pore size, specific surface area, etc. ( Figure 2 ).

[0020] 3. Capture of iodine vapor by conjugated column [5] aromatic derivative P5CBZ

[0021] 3.1 Solid vapor adsorption kinetics test

[0022] Before the test, the mass of a 2 mL empty bottle was weighed in advance. 5 mg of the activated macrocyclic P5CBZ was placed in a small vial. This was then placed in a 10 mL sample vial at 75°C under normal pressure. 5 mg of elemental iodine was placed in the vial. Every two hours, the vial was removed and the elemental iodine on the bottle wall was wiped clean. The total mass of the vial and the iodine-adsorbed macrocyclic was recorded on an electronic analytical balance. The same operation was repeated for 24 hours until the macrocyclic was found to be saturated with adsorption ( Figure 3 ).

[0023] 3.2 Heat loss analysis

[0024] Before the thermogravimetric experiment, the conjugated column [5] aromatic derivative P5CBZ was activated by heating in vacuum at 80 °C. Then, 5 mg of the sample was placed in a 2 mL vial. The vial opening was placed in a 5 mL vial containing 5 mg of iodine. The iodine vapor adsorption experiment was carried out at 75 °C ( Figure 4 After saturated adsorption, heat loss analysis was performed. The N2 flow rate was set at 40 mL / min, and the instrument temperature was increased at 25°C / min to 800°C. Testing revealed no significant weight loss between 25 and 400°C. Temperatures above 400°C correspond to the melting / decomposition point of the macrocyclic P5CBZ, demonstrating its excellent thermal stability and suitability for the high-temperature environments of nuclear power plants.

[0025] 3.3 Powder X-ray Diffraction

[0026] In order to study the transformation of the crystal structure of the conjugated columnar[5]arene derivative P5CBZ before and after the adsorption of iodine vapor, we performed powder X-ray diffraction analysis on its macrocycle before and after the adsorption of iodine vapor, such as Figure 5 As shown in the images, it can be clearly observed that the crystal structure of P5CBZ changes before and after the adsorption of iodine vapor. The characteristic peaks of the macrocycle disappear completely (III-P5CBZ crystal before adsorption, IV-P5CBZ crystal after adsorption), confirming that the iodine element causes the macrocycle to lose its crystallinity and that iodine is well dispersed in the pillar[5]arene. At the same time, it also indirectly illustrates the strong interaction between the iodine element and the pillar[5]arene, which completely changes the crystal phase structure of the macrocycle through strong charge transfer.

[0027] 3.4 UV absorbance test in iodine aqueous solution

[0028] First, prepare 1mmol / L iodine aqueous solution, dilute it to 250 μmol / L and place it in a 10ml vial. Take different weights of activated column [5] aromatic hydrocarbon P5CBZ and place it in 250 μmol / L iodine aqueous solution. At the same time, put in a magnetic bar and start stirring. After different time periods, test the absorbance of iodine water. The change in absorbance determines that P5CBZ also has a good adsorption effect on iodine in the aqueous phase ( Figure 6 ).

[0029] 3.5. Cyclic experiment of adsorption efficiency of P5CBZ after adsorption of iodine vapor.

[0030] The stability of column[5]arene P5CBZ after adsorption of iodine vapor was explored below. Figure 7 As shown in the figure, P5CBZ is first allowed to adsorb iodine vapor at 75°C to reach a saturated state, and the total mass of the macrocycle and the adsorbed iodine vapor is recorded. Then it is released in a n-hexane solvent. The figure shows that I2@P5CBZ tends to be stable with increasing number of times. The weight loss is large in the first few times, which may be due to the escape of iodine molecules physically adsorbed on the surface. After the fourth time, the weight loss tends to be slow, reaching a basically stable state.

[0031] Beneficial effects of the present invention:

[0032] 1. The carbazole-modified conjugated pillar[5]arene derivative of the present invention is obtained by Suzuki coupling reaction of a carbazole compound having a π conjugated group with pillar[5]arene. The conjugated pillar[5]arene derivative provides a good cavity structure that can encapsulate guest molecules of suitable size. Adsorption isothermal tests and cultivated single crystal structures show that the carbazole-modified ethyl pillar[5]arene transforms from a non-porous structure to a porous structure compared to conventional unmodified fully ethoxy pillar[5]arene, and significantly increases the specific surface area. It also forms one-dimensional channels in the stacking mode, making it suitable as a new adsorbent material for adsorbing guest molecules of matching size. Thermogravimetric tests also show that it has good thermal stability and can be used as a new adsorbent material for adsorbing iodine.

[0033] 2. Conjugated pillar[5]arene derivatives can not only adsorb iodine vapor from the air, but also from organic solvents or water. Compared with previously reported iodine adsorption materials, carbazole-modified ethyl pillar[5]arene is very simple to synthesize, uses relatively cheap raw materials, and has high thermal stability. Iodine is easily soluble in organic solvents, so the adsorbed iodine can be released in organic solvents and can be reused multiple times.

[0034] 3. Compared with the traditional unmodified ethoxylated pillar[5]arene as an adsorption material, due to the limitation of its own small cavity, it can only capture a small amount of iodine. However, the molecular stacking cavity of the pillar[5]arene modified with the large π conjugated group carbazole becomes larger and forms a one-dimensional channel, which greatly enhances the adsorption performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the crystal stacking pattern of P5CBZ.

[0036] Figure 2 This is a low-temperature nitrogen adsorption-desorption isotherm test.

[0037] Figure 3 Solid vapor adsorption kinetics test.

[0038] Figure 4 For thermal gravimetric test.

[0039] Figure 5 Powder X-ray diffraction.

[0040] Figure 6 It is the UV absorbance test in iodine aqueous solution.

[0041] Figure 7 This is a cyclic experiment of the adsorption efficiency of P5CBZ after adsorbing iodine vapor.

[0042] Figure 8 This is the H NMR spectrum of the conjugated column 5 aromatic derivative. DETAILED DESCRIPTION

[0043] The synthesis of P5CBZ of the present invention and its application as an adsorption material in iodine capture are further described below through specific examples.

[0044] Example 1: Synthesis of Conjugated Pillar 5 Arene Derivative P5CBZ

[0045] Trifluoromethanesulfonate-modified column[5]arene P5-OTf (296 mg, 0.3 mmol), 4-(9H-carbazol-9-yl)phenylboronic acid (74 mg, 0.6 mmol), Pd(PPh3)4 (35 mg, 0.03 mmol), LiBr (13 mg, 0.05 mmol) and K2CO3 (276 mg, 2.0 mmol) were added to toluene / EtOH / H2O (4 mL / 0.5 mL / 0.5 mL) and heated under reflux at 100 °C for 36 h under N2 protection. The reaction mixture was then cooled to room temperature and poured into water (30 mL). After extraction with CH2Cl2, the combined organic phases were dried over Na2SO4. P5CBZ was obtained by silica gel column chromatography (petroleum ether / CH2Cl2 / ethyl acetate = 50:1:2, v / v / v) as a white solid (98 mg, 63%). 1 H NMR (400 MHz, Chloroform- d ) δ 8.18 – 8.10 (m, 4H), 7.53 – 7.37 (m, 14H), 7.33 – 7.17 (m, 14H), 6.72 (s, 2H), 6.61 (s, 2H), 6.50 (s, 2H), 5.96 (s, 2H), 4.02 (s, 2H), 3.92 (s, 2H), 3.79 – 3.55 (m, 21H), 3.47 (s, 3H), 1.49 (s, 3H), 1.18 (s, 4H), 1.13 (d, J = 5.3 Hz, 10H), 0.89 – 0.82 (m,11H) ( Figure 8 ).

[0046] Its synthetic route is as follows:

[0047]

[0048] Example 2: Iodine capture test of conjugated column [5] aromatic derivative P5CBZ.

[0049] Before the test, the mass of two 2 mL empty bottles was weighed in advance. 5 mg of activated macrocyclic P5CBZ crystals and 5 mg of activated macrocyclic EtP5 crystals were taken respectively and placed in two vials. Then, they were placed in two 10 mL sample bottles under normal pressure and 75 °C. 5 mg of iodine was placed in each bottle. Every two hours, the vials were taken out and the iodine on the bottle wall was wiped clean. The total mass of the vials and the macrocyclic ring after iodine adsorption was recorded on the electronic analytical balance. The adsorption was found to be saturated and then compared. It was found that the traditional unmodified ethoxy column [5] aromatic hydrocarbon EtP5 crystals can only adsorb a very small amount of iodine. However, after testing, it was found that the crystals of the conjugated column [5] aromatic hydrocarbon derivative P5CBZ modified with carbazole had an iodine adsorption capacity of up to 3.1 g / g. This is far higher than that of the unmodified ethoxy column [5] aromatic hydrocarbon. The heat loss analysis of the thermogravimetric analyzer showed that the heat loss after adsorbing iodine vapor to saturation was as high as 30.1%. In powder X-ray diffraction analysis, it can be clearly observed that the crystal structure of P5CBZ changes before and after adsorption of iodine vapor. The characteristic peaks of the macrocycle disappear completely. The simple substance causes the macrocycle to lose its crystallinity and the good dispersion of iodine in the columnar[5]arene. The absorbance test in iodine aqueous solution also shows that P5CBZ has a good adsorption effect on iodine in aqueous solution.

Claims

1. A carbazole-modified conjugated pillar[5]arene derivative having the structural formula: 。 2. The method for synthesizing the carbazole-modified conjugated pillar[5]arene derivative according to claim 1, comprising the following steps: using toluene, ethanol and water as a mixed solvent, tetrakis(triphenylphosphine)palladium, triphenylphosphine and potassium carbonate as a co-catalyst, reacting pillar[5]arene trifluoromethanesulfonate and 4-(9H-carbazol-9-yl)phenylboronic acid at a molar ratio of 1:1 to 1:1.2 under nitrogen protection at 95-105°C for 24-36 hours, dissolving in distilled water, extracting with dichloromethane, drying with anhydrous sodium sulfate, and separating the organic phase by column chromatography to obtain a white solid, which is the target product, the carbazole-modified conjugated pillar[5]arene derivative; The structural formula of column[5]arene trifluoromethanesulfonate is: 。 3. The method for synthesizing the carbazole-modified conjugated pillar[5]arene derivative according to claim 2, wherein: The amount of tetrakis(triphenylphosphine)palladium used is 0.1 to 0.2 times the molar amount of column[5]aryl trifluoromethanesulfonate; the amount of triphenylphosphine used is 0.2 to 0.3 times the molar amount of column[5]aryl trifluoromethanesulfonate; and the amount of potassium carbonate used is 8 to 12 times the molar amount of column[5]aryl trifluoromethanesulfonate.

4. The method for synthesizing the carbazole-modified conjugated pillar[5]arene derivative according to claim 2, wherein: In the mixed solvent, the volume ratio of toluene, ethanol and water is 8:1:

1.

5. Use of the carbazole-modified conjugated column [5] aromatic hydrocarbon derivative as an adsorption material in iodine capture as claimed in claim 1.

6. The use of the carbazole-modified conjugated column [5] aromatic hydrocarbon derivative as an adsorption material in iodine capture as claimed in claim 5, characterized in that: Carbazole-modified conjugated columns[5] arene derivatives are used to adsorb iodine vapor, or adsorb iodine in organic solvents and water.

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